The invention relates to a valve in the form of a pipe as well as to a method for releasing and blocking a fluid stream by means of such a valve.
Basically, valves have a valve housing and, arranged therein, at least one valve closure member. Frequently, the valve closure member can be moved relative to a valve seat in a linear back-and-forth manner in order to close and open the valve seat in a controlled manner. Frequently, to actuate such valves, pull-type electromagnets are used whose armature moves the valve closure member against the force of a return spring away from the valve seat. Such magnets have a self-closing function. When the dimensions of the magnetic drive are established, care is taken that said drive is able to overcome the force of the return spring. Frequently, this results in relatively large and correspondingly power-demanding magnetic drives.
It has also been suggested to adjust the valve closure member via a motor-driven adjustment unit. The linear adjustment movement for the valve closure member is generated by the rotary motion of the motor, for example, via spindle lifting gears.
Considering such valves, it is relatively difficult to achieve a self-closing function that is required when the valve closes automatically in case of danger.
The self-closing function is mostly provided by return springs that, in the first-mentioned case, guide the pull-type electromagnet and, in the second-mentioned case, guide the motor adjustment drive out of the open position into the closed position. The correspondingly heavily dimensioned return springs can result in a shock-like, hard placement of the valve closure member on the valve seat and, in the course of time, cause damage there.